Many methods exist for removing an undesired material from an environment. For instance, numerous products are available commercially for removing spilled liquids from a surface. Some such products are used to remove oil from open water, such as when an oil spill has occurred. In this application, it is desirable to selectively remove oil from water. For such absorbents, efforts are sometimes made to increase the selectivity of oil over water.
Currently available products for spill control include clay, kaolin, illite, bentonite, diatomite, hectorite, montmorillonite, attapulgite, silica, silica sand, polypropylene, sodium polyacrylate/polyacrylamides, vermiculite, gypsum, limestone, metal oxides, asphalt, fiberglass, diatomaceous earth, perlite and other materials. Such materials, while satisfactory in function, suffer from certain drawbacks. Many such products contain silica, which poses a hazard to humans. In addition, most such materials are not biodegradable, which is a factor that can limit the options for disposal of the used sorbent material.
There are also several organic spill control products described in the art. Examples of such materials include natural fibers such as grass, pre-cooked cereal kernels, sawdust, cellulose, and peat. U.S. Pat. No. 5,492,881 purports to describe a cellulose based sorbent system, where the cellulose has been treated with an additive to render it both hydrophobic and oleophilic so it will selectively remove oil from water. U.S. Pat. No. 4,969,774 purports to describe the use of pre-cooked and puffed cereals for oil removal. Another document, U.S. Pat. No. 5,399,350, purports to disclose a particulate milled seed material in which the lipids have been removed through solvent extraction and wherein the material is designed to remove and disperse oil from open water and solid surfaces. The composition is a solvent-extracted proteinaceous material derived from grain products having oil sorptive properties. Also, U.S. Pat. No. 5,492,881 purports to describe the use of diatomaceous earth, clay, silica, corncob, peatmoss, perlite, polypropylene, sawdust, cellulose, polystyrene, vermiculite, peat and cork to absorb liquids. This composition is taught as a general absorbent; in this document, it is stated that materials that absorb both water and oil are undesirable. U.S. Pat. No. 5,891,937 purports to disclose the use of corn stalks, husks, cobs, and kernels as carriers. U.S. Pat. No. 6,110,323 purports to disclose the use of delignified waste from hulls, straw, stover, and shells as a carrier. Other carriers are purportedly disclosed in U.S. Pat. Nos. 6,383,609 and 6,391,120. Generally, other biodegradable materials such as peat moss, sawdust, hair, feathers, cotton, cork, starch, bagasse, seeds, seed hulls, and other seed components have also been proposed.
Many methods for introducing a material into an environment also are known. In many cases, it is desired to introduce the material in a delayed-release manner, by which is contemplated that at least some of the material is bound up with another material or otherwise is not immediately available to function in the environment for its intended purpose. For instance, it is often desired to introduce a control agent, i.e., a material that limits the growth or spread of a living thing, into an environment. Known control agents, such as insecticides, larvicides, rodenticides, fungicides, and so forth may be oil-based or water-based. It is desirable to provide a sorbent for such control agents, and in particular, it is desirable to provide a sorbent that allows delayed release of at least some control agents into an environment. Further, it is highly desirable to provide a sorbent that is useful in sorbing both oil- and water-based control agents.
Typical control agents are provided in liquid or solid form. There are advantages and disadvantages to each product form. Liquid pesticides can be applied as a spray, which is advantages in some respect. Drift control of the spray can be a challenge, however, especially in an aerial broadcast application. Solid pesticide products are better at targeting an area for pest control, because there is less drift of the solid product. Pelleted or compacted compositions are typically used in solid pesticide products. The majority of such composition is composed of a carrier or absorbent material, and the active ingredient is usually a small percentage (<10%) of the pellet weight. Another advantage of a solid control agent composition is that the weight of the composition allows penetration into vegetative areas that are less accessible via a liquid spray. Heavier pellets often can penetrate through a tree canopy, whereas liquid droplets would tend to coat and contaminate the tree canopy.
One drawback to many known solid pesticides products is that non-biodegradable carriers often are used in such products. These carriers can lead to contamination of the area of treatment. In recognition of this problem, numerous biodegradable carriers have been provided; examples include materials such as corncob, peanut hulls, and starches. Many known biodegradable carriers are unsatisfactory. In many cases, the resulting composition does not perform as well as a non-biodegradable product. In addition, many biodegradable materials such as corncob, peanut hulls, and starches do not disperse easily when in contact with water, leaving a contaminant residue. Corncob is especially poor in this regard, because it has low density as well as poor dispersibility in water. In addition, when a granular pesticide does not readily disintegrate in an aquatic environment, the active ingredient is not readily released and thus a less efficacious pest control product with residual contaminant pesticide activity is provided.
In the case of mosquito larvicides, such materials ordinarily are released into standing or slowly moving water to destroy larvae growing in the water. It is particularly preferred that the carrier should release at least a portion of the larvicide within the topmost two feet of water in a standing or slowly moving water column, where most or all of the larvae are found. It is further preferred that the larvae in the water column be destroyed within 24 hours, and preferably within 8 hours of treatment. Although the prior art has provided numerous carriers for control agents, not all carriers allow for the preparation of a control agent composition that meets these preferred criteria.
In a first preferred embodiment of the invention, it is a general object to provide a sorbent that is useful in conjunction with the introduction of a material into an environment. In a second preferred embodiment of the invention, it is a general object to provide a sorbent that is useful in conjunction with the removal of a material from an environment, the material being removed by sorption of the material into the sorbent and removal of the sorbed composition thus formed from the environment.